The Prince of Wales has hit out at critics who refer to him as a “potty” royal, but has admitted he talks to trees and plants as if they were his children.

In a remarkably candid interview for a BBC documentary, Prince Charles dismisses suggestions he is “loony” but confesses to lying on the floor at his Highgrove home to eavesdrop on visitors.

During the hour-long programme, he is seen wandering around the extensive grounds of the Gloucestershire estate with gardener Alan Titchmarsh.

According to the News of the World, he tells the presenter: “I got a lot of flak for a lot of things. I mean, bewildered, frankly, as though you were doing something positively evil. I mean potty this, and potty that, loony this and loony that.”

But he admits: “I have eavesdropped on what the visitors have said.” He reportedly tells Titchmarsh: “When they're going round outside the windows sometimes you've got to lie on the floor.” And he describes speaking to shrubbery as something which keeps him “relatively sane”.

“I happily talk to the plants and the trees, and listen to them. I think it's absolutely crucial,” he is reported to say.